1. Field of the Invention
The present invention relates to an information processing apparatus, an information processing method, and a supply medium, more particularly to an information processing apparatus and an information processing method, which can change the tempo of audio information synchronously with changes of tempo (speed of a tune) for an instrumental accompaniment composed of MIDI (Musical Instruments Digital Interface) information, as well as a supply medium.
2. Background of the Invention
The official gazette of Japanese Patent Laid-Open No.8-234791 has disclosed a musical reproducing apparatus, which can change the tempo of a chorus synchronously with changes of the tempo for an instrumental accompaniment composed of MIDI information without any change of pitches (frequencies). Hereunder, this apparatus will be described with reference to FIG. 20.
The user enters the tempo of a tune from a tempo input block 101. The tempo input block 101 then supplies a tempo change signal corresponding to the entered tempo to the MIDI reproducing block 101 and the chorus reproducing block 103.
The MIDI reproducing block 102 is composed of an accompaniment reproducing block 111 and the accompaniment reproducing block 111 reproduces supplied accompaniment music information (MIDI information), thereby generating accompaniment music signals. The generated accompaniment music signals are supplied to a mixer 104.
The chorus reproducing block 103 is composed of an expanding block 121, a periodicity analyzer 122, a unit periodic data memory 123, and a chorus expanding/thinning-out block 124.
The expanding block 121 expands chorus information compressed with the use of, for example, such a data compression method as MPEG (Moving Picture Experts Group) to audio signals encoded with the PCM (Pulse Code Modulation) method. Decoded chorus information is then supplied to both periodicity analyzer 122 and chorus expanding/thinning-out block 124.
The periodicity analyzer 122 recognizes strong periodicity in the supplied chorus information and extracts one strong period therefrom. The extracted unit periodic data is supplied to the unit periodic data memory 123 and stored there. The stored unit periodic data is read and supplied to the chorus expanding/thinning-out block 124 as needed.
The chorus expanding/thinning-out block 124 generates reproduction chorus signals from chorus information according to the tempo change signal and the unit periodic data supplied respectively. For example, when no tempo is changed, the chorus expanding/thinning-out block 124 outputs supplied chorus information as audio signals without adding any data to nor thinning out any part from the supplied information. If the tempo change signal specifies acceleration of the tempo, however, the chorus expanding/thinning-out block 124 thins out the number of unit periodic data items corresponding to the specified acceleration from the strong periodicity part of the information so as to speed up the tempo. On the contrary, if the tempo change signal specifies slow-down of the tempo, the chorus expanding/thinning-out block 124 adds the number of unit periodic data items corresponding to the specified slowdown to the strong periodicity part of the information so as to slow down the tempo. The tempo of the chorus can thus be changed following up with the change of the accompaniment music without changing pitches of the chorus.
The mixer 104 mixes supplied accompaniment music signals with chorus signals. The mixed signals are then supplied to the amplifier 105. The amplifier 105 mixes the supplied signals with singing voices entered via a microphone 107, then outputs the mixed signals as sounds from a speaker.
In such an information reproducing apparatus as described above, however, characteristics of chorus signals are used to change a tempo. This is why the apparatus, which has not coped with other signals, has been not applied to those signals.
Furthermore, the above apparatus has also been confronted with a problem that a delay time from an accompaniment music is generated if a long time is taken for decoding chorus information, as well as for changing a tempo.